Question

I’m trying to do regular expression in PHP but I keep getting bugged. I want it so it’s A-Z, 0-9, and the underscore (_) but the underscore cannot be used on the edges of a text. Only on the inside.

Here is waht I have:

if (!ereg("^[a-zA-Z0-9_]{3,16}$",$username)) {
// Does not match
}else{
// Good job, within rules!
}

Answer 1

I’m not sure if this is the best way to do it, but it should work:

^[a-zA-Z0-9][a-zA-Z0-9_]{1,14}[a-zA-Z0-9]$

I decreased your bounds by 2 because you are accounting for two characters at the beginning/end of the string.